1. Field of Invention
This invention relates to a spike device for a sole of an anti-slid shoe. The invention also relates to a shoe comprising such a spike device.
2. Description of Related Art
Shoes equipped with spikes are used for getting a good grip on slippery surfaces. Typically, spiked shoes are useful for people walking on streets or pavements covered with snow and ice and for golfers. Conventional spiked shoes suffer from the drawback that the spikes are in constant contact with ground surface during wear, also in situations where spikes are not necessary, such as on hard surfaces, or where spikes are unsuitable, such as on most indoor floors. This causes excessive wear on the spikes and certain surfaces or makes a frequent switching of shoes necessary.
To overcome these disadvantages various examples of shoes with retractable spikes has been proposed over the years. U.S. Pat. No. 4,873,774 discloses one example where a fluid pressure is used to push cleats to extend from the sole bottom. Another example is disclosed in U.S. Pat. No. 5,299,369 where pneumatically actuated, rotatable spikes are used. Still another example is disclosed in U.S. Pat. No. 6,058,627 where spikes are slidable between a retracted and an extended position. Still another example is disclosed in U.S. Pat. No. 6,125,556 where high pressure liquid is used to extend the spikes.
SE 524692 discloses a system where hydraulically actuated and controlled lifting pads placed under the outer sole are arranged to expand such that spikes mounted to the outer sole loose contact with the ground.
U.S. Pat. No. 4,375,729 discloses a footwear having spikes attached to flexible recesses or dimples of the sole, wherein a sliding cam member is used to urge the spikes from a retracted to an extended position.
WO 2007/037731 discloses a structure where an upper and lower sole are movable in relation to each other and where a slidable locking plate is used to lock the soles in relation to each other. Springs are used for forcing the soles apart such as to retract the spikes. GB 2420485 discloses a similar structure, but without locking function, where partly retracted spring-suspended sole nails are forced to protrude by applying a pressure onto the upper sole.
General problems associated with the known shoes with retractable spikes are a complex structure, a low structural strength and/or functioning problems when exposed to dirt. Thus improvements are still needed in this field.